Table 2.
Odds ratios (95% confidence intervals) for the risk of an SLE flare in the year after the HCQ measurement at time zero (T0) (N=660).
| SLE flare within one year |
||||
|---|---|---|---|---|
| Overall N=660 | N(%) or mean (SD) N=191 | Univariate OR (95%CI) |
Multivariate OR (95%CI) |
|
|
| ||||
| Demographic data and comorbidities | ||||
| Age at serum sample, years, mean (SD) | 36.2 (13.5) | 33.3 (12.2) | 0.98 (0.96–0.99) | 0.98 (0.97–0.99) |
| Male sex | 580 (87.9) | 167 (87.4) | 1.06 (0.63–1.75) | - |
| Black ethnicity | 107 (16.2) | 47 (24.6) | 2.22 (1.45–3.40) | 2.09 (1.33–3.26) |
| Education level | ||||
| Post-secondary | 413 (62.6) | 116 (60.7) | Reference | Reference |
| ≤High school | 247 (37.4) | 75 (39.3) | 1.12 (0.79–1.58) | 1.10 (0.76–1.58) |
| Cigarette smoking | ||||
| Non-smoker | 437 (66.2) | 127 (66.8) | Reference | |
| Current or past smoker | 222 (33.6) | 63 (33.2) | 0.97 (0.67–1.38) | |
| Body mass index, kg/m2, mean (SD) | 25.8 (6.1) | 25.9 (6.0) | 1.00 (0.98–1.03) | |
| SLEDAI-2K at T0, mean (SD) | 4.8 (4.9) | 5.9 (5.7) | 1.06 (1.02–1.10) | 1.05 (1.01–1.09) |
| Treatment at T0 | ||||
| Corticosteroids | 438 (66.4) | 137 (71.7) | 1.42 (0.99–2.06) | 1.00 (0.67–1.51) |
| Azathioprine | 91 (13.8) | 38 (19.9) | 1.95 (1.23–3.07) | 1.63 (0.99–1.51) |
| Hydroxychloroquine level | ||||
| Severe HCQ non-adherence | 48 (7.3) | 28 (14.7) | 3.86 (2.12–7.12) | 3.32 (1.78–6.28) |
| Non-quantifiable | 28 (4.2) | 16 (8.4) | 3.48 (1.62–7.67) | |
Results are expressed as N (%) for categorical variables and means (SD) for continuous variables. An SLE flare was defined by occurrence of one of the following events in the first year after the T0 visit: (a) ≥4-point in the SLEDAI-2K; (b) new start in prednisone (oral or pulsed) or other immunosuppressive agent (azathioprine, methotrexate, mycophenolate mofetil, rituximab, oral or IV cyclophosphamide); (c) new renal involvement including active nephritis, new nephrotic syndrome, new dialysis, or kidney transplantation.
Following variables were included in the multivariate model: age, black ethnicity, education level (post-secondary; ≤High school), SLEDAI-2000, corticosteroids, azathioprine, and severe HCQ non-adherence. No interaction was found between nonadherence to HCQ and age (P=0.51), education (P=0.47), Black ethnicity (P=0.26), SLEDAI-2K (P=0.59), azathioprine (P=0.23), or with corticosteroids (P=0.49)
Abbreviations: SD: standard deviation; OR: odds ratio; 95% CI: 95% confidence interval; kg/m2: kilograms per square meter; SLEDAI-2K: SLE disease activity index 2000; HCQ: hydroxychloroquine;